Beginning February 24th, Google officially updated its display url AdWords policy regarding multiple urls in each ad group. Previously, multiple display urls were allowed in a single ad group. Now, only one display url is permitted in each ad group. This amendment applies to all advertisers, regardless of any previous exceptions.
According to The Official Google Blog, the change was made in an effort to provide more relevant search results for Google users. By having the same high level domain name for each ad group, users search experiences will be enhanced.
This update only applies to top-level domains. For example, if you have a domain www.shoes.com and www.shoes.com/shoes in the same ad group, both would be permitted. On the other hand, if you have the display urls, www.shoes.com and www.freeshoes.com, they would not be permitted as they do not have the same root domain.
Google recommends separating ad groups with multiple domains into separate and unique ad groups. By doing so, you will not only comply with the policy modifications; you can also track the performance of your domains in a more efficient manner.
The display url and the destination url should still match. The other requirements regarding urls will remain unchanged. For more information on Google’s display url policies, you can visit the AdWords Help center.